I get a high pitched whine from the back of the brake servo when I release the foot brake, is it a vacuum/air leak and can it be fixed with the servo in place.

I'd have to agree with Jakesmuscle.
A hard brake pedal is usually due to the brake servo - the vacuum - not working properly.

Check the hoses on the servo unit for splits or perishing.

A quick check you can do is, with the engine idling, spray a light oil around your brake servo unit. If you get 'blue smoke' from your exhaust this can point to an air leak in the servo unit. The oil has been sucked in via an air leak and burnt ..

• Brake Switch (Cruise Control) Clutch Switch
  
• Cruise Control Module
• Cruise Control Servo Cruise Control Switch
  
• Release Valve
• Vacuum Pump
• Vacuum Vent ValveVacuum System, Checking For Leaks
  • Remove vacuum hose from vacuum pump seal off.
  • Remove lower instrument panel cover, left.
  • Push servo unit diaphragm in, to do this press brake pedal down by hand until pressure point.
  • Then release brake pedal.
  The diaphragm must not move.
  
  NOTE: Malfunctions can be caused by an incorrectly adjusted vent valve, leaking servo unit or through cracks in the vacuum hoses.Here is a quick run down of the components I need more info to help u more is ur car a syncro or a sedan is ur engine a 1.8, 1.9 or 2.8
  

• Brake Switch (Cruise Control) Clutch Switch [img src="http://i.fixya.net/uploads/images/no-p.gif">
• Cruise Control Module
• Cruise Control Servo Cruise Control Switch
• Release Valve
• Vacuum Pump
• Vacuum Vent ValveVacuum System, Checking For Leaks
  Remove vacuum hose from vacuum pump seal off.
  • Remove lower instrument panel cover, left.
  • Push servo unit diaphragm in, to do this press brake pedal down by hand until pressure point.
  • Then release brake pedal.
  The diaphragm must not move.
  
  NOTE: Malfunctions can be caused by an incorrectly adjusted vent valve, leaking servo unit or through cracks in the vacuum hoses.Here is a quick run down of the components I need more info to help u more is ur car a syncro or a sedan is ur engine a 1.8, 1.9 or 2.8

Check condition and operation of idle control valve.
Also check condition of vacuum lines and brake vacuum assist hose and vacuum assist servo.

To check if you have a vacuum leak before the servo unit, first check hoses and connections, then pull off the vacuum hose to the servo unit and put your thumb on the end of it. You should feel a strong pull/vacuum. If you release your thumb then you should hear the engine revs climb, and then possibly go back to normal.
If you feel lack of vacuum, then you likely have a leak somewhere.

Another thing to check is that when you pump the brakes several times, the engine note changes and your brakes become stiff for a second or two before becoming softer again.
After you have run the engine for a few seconds and then turned it off you should be able to pump the brake pedal three times, with it being soft-ish each time until all vacuum has been spent from the servo unit, and then your brakes become stiff again. If this seems not to be the case, and they are still all the time, then you have a vacuum leak, possibly in the servo unit.

The most common cause would be a defective power steering pump.

It may be your brake vacuum assisted booster is leaking. Have it checked out.

hi.
the most likely cause is a damaged vacuum pipe between the inlet manifold, and the brake servo unit.
this would account for the missing and idling, due to the extra air getting into the engine.
it will also account for the brake hardness as there will be no vacuum to the servo unit.

the pipe is probably between 1/2" and 3/4" diameter and go from the inlet manifold to the brake servo unit on the bulkhead. make sure this pipe is not split or damaged and it is connected securely at both ends.

it is possible that the manifold gasket is leaking, but it would be very unusual for this to happen unless the manifold has been disturbed

not normal at all,a couple of causes 1 small valve at the front of the servo unit,2busted pipe coming from the servo unit,3the servo unit itself needs replaced.so where is the servo unit?.if you lift the hood you will see in front of the brake pedal only inside the engine compartment look closely and try to judge it ,its about the size of a bottom of a small sauspan only about 4/5 times the thicknes,thats your servo and that where your problem is.adrian,,,

hi from uk the symptoms you clearly describe sound like your brake servo /vacuum cylinder is at fault ie whilst brake pedal is off all is ok ? but when pedal pressed engine falters? this is a sign that the seal on the vac piston inside the servo unit is allowing air /atmospheric air to enter the servo as you brake and this assists braking however when inner pistonseal is leaking at some point inside the servo bore ie a scoared or rusty point ?the atmospheric air passes the piston/seal and so the vacuumpipe to servo is drawing this air into inlet manifold resulting in upsetting fuel mixture ie weak too much air ratio to fuel resulting inshaking engine you describe ? try this?? if you disconnect vac pipe from servo unit then seal off the pipe with thumb then ask assistant to start engine then it should run ok ? also it should be ok when b/pedal pressed remember there will be no vac assistance ?? if above test prove right ? then you will req a new servo unit only not complete master cylinder too ? you can diy this then bleed brakes after replacing servo ? hope this helps

you may have a vacuum leak, this will cause the engine to inhale excess air and when you put your foot on the brake, which is vacuum assisted, it stalls the engine.Check your vacuum lines at the cruise servo( behind the battery) , up to the throttle body, also, check vacuum at the EGR valve and at the front of the engine where the belts run, there is a line that crosses to the fender wall there. Hope this helps.
R